Turn waste into food! Efficient synthesis of starch and protein from corn stalk.
The joint team used the multi-enzyme molecular system containing cellulose degrading enzyme and starch synthase in vitro to biotransform with Saccharomyces cerevisiae, which can hydrolyze cellulose in corn stalk with high efficiency to synthesize artificial starch, and at the same time produce microbial protein by low-cost fermentation under aerobic conditions.
The rapid growth of global population and climate change will make mankind face great challenges to food security. Using synthetic biotechnology to efficiently convert agricultural waste resources into artificial food is one of the important ways to alleviate the food crisis and realize the sustainable development of agriculture.
Recently, Tianjin Institute of Industrial Biotechnology of China Academy of Sciences, together with Institute of Biotechnology of Chinese Academy of Agricultural Sciences, developed a new technology to efficiently synthesize artificial starch and single cell protein from corn stalk, which further reduced the production cost of artificial starch and provided a new way for grain production. Related research papers were published online in Science Bulletin (English version).
Producing starch from lignocellulose is expected to alleviate the food crisis.
The world produces about 200 billion tons of lignocellulose every year. Because each ton of lignocellulose contains about 40% cellulose, it produces about 80 billion tons of cellulose every year.
"Human beings can digest dextran linked by α-1,4-glycosidic bonds, that is, starch, but due to the lack of cellulose hydrolase, they cannot digest dextran linked by β-1,4-glycosidic bonds, such as cellulose, from lignocellulose. If the glucan composed of β-1,4-glycosidic linkage can be converted into the glucan composed of α-1,4-glycosidic linkage through enzymatic reaction, that is, using non-food biomass to produce starch is expected to alleviate the food crisis, which will be a great benefit for human beings. " Ma Yanhe, one of the authors of the paper and a researcher at Tianjin Institute of Industrial Biotechnology of China Academy of Sciences, said.
Developing multi-enzyme molecular system in vitro to improve the production efficiency of artificial food
In this study, in vitro multi-enzyme molecular system containing cellulose degrading enzyme and starch synthase was used for biotransformation with Saccharomyces cerevisiae. Cellulose in corn stalk could be hydrolyzed with high efficiency to synthesize artificial starch, and microbial protein could be produced by low-cost fermentation under aerobic conditions.
"In this study, we first created a low-cost efficient cellulose degradation and cellobiose production technology to remove β -glucosidase from commercial cellulase, effectively removed β -glucosidase from cellulase mixture, and used cellulose-enzyme-yeast complex to reduce the feedback inhibition of cellulose hydrolysate and improve the hydrolysis ability of cellulase." Zhang Wei, one of the authors of the paper and a researcher at the Institute of Biotechnology of the Chinese Academy of Agricultural Sciences, said.
Zhang Yiheng, a researcher at Tianjin Institute of Industrial Biotechnology, China Academy of Sciences, said: "Traditional biological manufacturing relies on living organisms such as microorganisms, plants and animals, but a lot of energy and sugar resources are used for self-reproduction, replication and life maintenance of organisms unrelated to biological manufacturing, which restricts the improvement of manufacturing efficiency. In vitro multi-enzyme molecular system is a new tool of synthetic biology, which completely avoids the above unnecessary waste and greatly improves the energy utilization rate, just as machinery replaces cattle in agricultural production, making it possible to achieve high production efficiency of artificial food. "
"One of the important technological breakthroughs in this research is the preparation of intracellular recombinant enzyme at low cost. The team transformed the recombinant enzyme expression strain, used cheap inorganic nitrogen source and glucose culture medium to carry out microbial culture at ultra-high density, and reduced the production cost of key recombinant enzymes to near the lowest theoretical value, achieving the production cost per kilogram of recombinant enzyme (dry weight) of only 250 yuan, which reduced the enzyme cost by about 1 million times compared with laboratory shake flask fermentation and conventional enzyme purification technology; The second breakthrough is that on the basis of using the existing low-cost cellulase, after removing β -glucosidase by new technology, cellulose can be hydrolyzed efficiently, stably and controllably, and its cost is nearly 1 million times lower than that of expensive purified cellulase. " Zhang Yiheng said.
This new technology has opened up a new way for the production of artificial grain, achieved the goal of securing China’s rice bowl with cutting-edge new technology, and realized "storing grain in technology, storing grain in mountains and storing grain in forests", which is expected to solve the economic dilemma of grain storage and consolidate the foundation of food security in China. (Ma Aiping)
Source: Science and Technology Daily
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